what is doppler effect

The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the source of the wave. This phenomenon was named after the physicist Christian Doppler, who described it in 1842. It can be observed for any type of wave, including water waves, sound waves, and light waves. The Doppler effect is used in various applications, such as radar to measure the velocity of detected objects, and it is also of intense interest to astronomers who use the information about the shift in frequency of electromagnetic waves produced by moving stars to derive information about those stars and galaxies. The Doppler effect works on both light and sound objects, and it is based on the relative motion between a wave source and its observer.